an increase in crimes of
violence during the warmer years. An examination of European and
American statistics shows that the number of homicides decreases as we
pass from hot to cooler climates. Holzendorf calculates that the number
of murders committed in the Southern States of North America is fifteen
times greater than those committed in the Northern States. A low
temperature, on the contrary, has the effect of increasing the number of
crimes against property, due to increased need, and both in Italy and
America the proportion of thefts increases the farther north we go.

_Density of Population._ The agglomeration of persons in a large town is
a certain incentive to crimes against property. Robbery, frauds, and
criminal associations increase, while there is a decrease in crimes
against the person, due to the restraints imposed by mutual supervision.

"He who has studied mankind, or, better still, himself [writes my
father], must have remarked how often an individual, who is
respectable and self-controlled in the bosom of his family, becomes
indecent and even immoral when he finds himself in the company of a
number of his fellows, to whatever class they may belong. The
primitive instincts of theft, homicide, and lust, the germs of
which lie dormant in each individual as long as he is alone,
particularly if kept in check by sound moral training, awaken and
develop suddenly into gigantic proportions when he comes into
contact with others, the increase being greater in those who
already possess such criminal tendencies in a marked degree."

In all large cities, low lodging-houses form the favourite haunts of
crime.

_Imitation._ The detailed accounts of crimes circulated in large towns
by newspapers, have an extremely pernicious influence, because example
is a powerful agent for evil as well as for good.

At Marseilles in 1868 and 1872, the newspaper reports of a case of child
desertion provoked a perfect epidemic of such cases, amounting in one
instance to eight in one day.

Before Corridori murdered the Head-master of his boarding-school, he is
said to have declared: "There will be a repetition of what happened to
the Head-master at Catanzaro" (who had been murdered in the same way).

The anarchist Lucchesi killed Banti at Leghorn shortly after the murder
of Carnot by Caserio, and in a similar manner. Certain forms of crime
which become common at given pe